1. Field of the Invention
The present invention relates to a clutch mechanism of a coat film transfer tool and a coat film transfer tool having such clutch mechanism, and more particularly to a clutch technology for synchronizing the payout speed and takeup speed of coat film transfer tape in payout reel and takeup reel, in a coat film transfer tool having mechanism for transferring a coat film such as corrective paint layer or adhesive layer on a coat film transformer tape onto a sheet of paper or the like, and collecting the coat film transfer tape automatically after use.
2. Description of the Related Art
An example of construction of this kind of coat film transfer tool is shown in FIG. 20, in which the transfer tool comprises a payout reel (c) containing a roll of a coat film transfer tape (b), and a takeup reel (d) for recovering the coat film transfer tape (b') after use, rotatably provided in a case (a) to be held and manipulated by one hand, and a coat film transfer head (f) for pressing the coat film transfer tape (b) to the transfer area is projecting from the end of the case (a). Both the reels (c), (d) are mutually linked through a linkage (g), and the takeup reel (d) is of an automatic takeup type. This linkage (g) is constructed such that engaged with gears (h), (i) provided outside of the reels (c), (d) are engaged with each other. When this coat film transfer tool is used as an erasing tool for correcting an error, the case (a) is held by one hand, and the coat film transfer tape (b) is tightly pressed against the correction area (transfer area) by a pressing section (j) of the head (f), while the case (a) is moved in a specified direction. As a result, the corrective paint layer on the coat film transfer tape (b) in the pressing section (j) of the head (f) is applied on the correction area to cover and erase the letter or the like, and the coat film transfer tape (b') after use is automatically taken up and recovered on the takeup reel (d).
In this case, as used repeatedly, the outside diameter of the coat film transfer tape (b) on the payout reel (c) decreases, while the outside diameter of the coat film transfer tape (b') on the takeup reel (d) increases. On the other hand, the ratio of rotation of the payout reel (c) and takeup reel (d) (corresponding to the gear ratio of the linkage (g)) is always constant. Therefore, the takeup speed of the takeup reel (d) tends to be faster in the course of time as compared with the payout speed of the payout reel (c), and to prevent this, the payout speed and takeup speed must be synchronized. For this purpose, the payout reel (c) is provided with a clutch mechanism (k) for synchronizing the payout speed and takeup speed.
That is, in the payout reel (c), a boss (m) of a drive gear is rotatably supported on a support shaft (n), and a tape payout core (o) winding the coat film transfer tape (b) thereon is rotatably fitted in the boss (m), and the clutch mechanism (k) is disposed between the boss (m) and tape payout core (o).
This clutch mechanism (k) includes clutch pawls (p), (q) elastically deformable in the radial direction disposed on the outer circumference of the boss (m), which are elastically and detachably engaged with multiple catches (q), (q), . . . , provided in the inner circumference of the tape payout core (o)
When the takeup speed becomes relatively faster than the payout speed in the course of time, the synchronism of two speeds is broken and the rotary torque acting on the tape payout core (o) becomes large, the clutch mechanism (k) is actuated and the tape payout core (o) slips on the boss (m), so that the payout speed is synchronized with the takeup speed.
In such clutch mechanism (k), in the engaging and disengaging action between the clutch pawls (p), (q) and catches (q), (q), . . . , since elastic clicking sound is repeated intermittently, it may be uncomfortable for the user, and running of the coat film transfer tape (b) may be uneven, and this engaging and disengaging action becomes more frequent as the consumption is advanced and the difference between the payout speed and takeup speed becomes larger, and hence discomfort and uneven running become more and more obviously, and further improvements have been demanded.
In this regard, the present inventors previously proposed a clutch mechanism (r) as shown in FIG. 21 (see, for example, Japanese Laid-open Patent No. 5-58097). In this clutch mechanism (r), an elastic friction member (s) such as O-ring is interposed between the outer circumference of the boss (m) and the inner circumference of the tape payout core (o) in friction engaged state.
According to this clutch mechanism (r), in the synchronizing action, the three members (m), (s), (o) relatively slide smoothly, and so that discomfort and uneven running due to elastic and intermittent repeating actions can be eliminated.
In the structure of this clutch mechanism (r), however, since its force transmission makes use of frictional force by radial load among the three members (m), (s), (o), the designing and manufacturing conditions of the friction member (s) are very strict, and manufacture is difficult, which made it hard to lower the manufacturing cost.
That is, if the frictional force is too strong, the sense of manipulation tends to be too heavy in the latter half of the use. On the other hand, if the frictional force is too weak, the sense of manipulation tends to be too weak in the initial phase of use. Therefore, the frictional force must be set at an optimum value in consideration of such relation.
To obtain the optimum value of frictional force, when designing and manufacturing the friction member (s), its inside diameter and outside diameter must be respectively matched with the outer circumference of the boss (m) and the inner circumference of the tape payout core (o), and since the friction member (s) itself is also elastic, the thickness dimension of its radial direction must be also taken into consideration. Accordingly, after assembling the clutch mechanism (r), a process for fine adjustment of the shape and dimensions of the friction member (s) is additionally necessary.
Still more, since the diameter of the friction member (s) is set strictly, the friction member (s) must be assembled by force between the outer circumference of the boss (m) and the inner circumference of the tape payout core (o), and the assembling work is accompanied by much difficulty.